Natural oils, such as seed oils, and their derivatives can provide useful starting materials for making a variety of chemical compounds. Because such compounds contain a certain degree of inherent functionality that is otherwise absent from petroleum-sourced materials, it can often be more desirable, if not cheaper, to use natural oils or their derivatives as a starting point for making certain compounds. Additionally, natural oils and their derivatives are generally sourced from renewable feedstocks. Thus, by using such starting materials, one can enjoy the concomitant advantage of developing useful chemical products without consuming limited supplies of petroleum. Further, refining natural oils can be less intensive in terms of the severity of the conditions required to carry out the refining process.
Natural oils can be refined in a variety of ways. For example, processes that rely on microorganisms can be used, such as fermentation. Chemical processes can also be used. For example, when the natural oils contain at least one carbon-carbon double bond, olefin metathesis can provide a useful means of refining a natural oil and making useful chemicals from the compounds in the feedstock.
Metathesis is a catalytic reaction that involves the interchange of alkylidene units among compounds containing one or more double bonds (e.g., olefinic compounds) via the cleavage and formation of carbon-carbon double bonds. Metathesis may occur between two like molecules (often referred to as “self-metathesis”) and/or it may occur between two different molecules (often referred to as “cross-metathesis”). Self-metathesis may be represented schematically as shown below in Equation (A):Ra—CH═CH—Rb+Ra—CH═CH—RbRa—CH═CH—Ra+Rb—CH═CH—Rb,  (A)wherein Ra and Rb are organic groups.
Cross-metathesis may be represented schematically as shown below in Equation (B):Ra—CH═CH—Rb+Rc—CH═CH—RdRa—CH═CH—Rc+Ra—CH═CH—Rd+Rb—CH═CH—Rc+Rb—CH═CH—Rd,  (B)wherein Ra, Rb, Rc, and Rd are organic groups. Self-metathesis will also generally occur concurrently with cross-metathesis.
In recent years, there has been an increased demand for environmentally friendly techniques for manufacturing materials typically derived from petroleum sources, which can be made by processes that involve olefin metathesis. This has led to studies of the feasibility of manufacturing biofuels, waxes, plastics, and the like, using natural oil feedstocks, such as vegetable and/or seed-based oils. In at least one example, metathesis catalysts can be used to manufacture candle wax, which is described in PCT Publication No. WO 2006/076364, and which is herein incorporated by reference in its entirety. Metathesis reactions involving natural oil feedstocks or compounds derived from them also offer promising solutions for today and for the future.
Natural oil feedstocks of interest include, but are not limited to, oils such as natural oils (e.g., vegetable oils, fish oils, algae oils, and animal fats), and derivatives of natural oils, such as free fatty acids and fatty acid alkyl (e.g., methyl) esters. These natural oil feedstocks may be converted into industrially useful chemicals (e.g., waxes, plastics, cosmetics, biofuels, etc.) by any number of different metathesis reactions. Significant reaction classes include, as non-limiting examples, self-metathesis, cross-metathesis with olefins, and ring-opening metathesis reactions. Non-limiting examples of useful metathesis catalysts are described in further detail below.
Many specialty chemicals and chemical intermediates are derived from refining petroleum products. Such processes generally involve cracking and refining crude petroleum to obtain olefin fragments having a small number of carbon atoms (e.g., two or three carbons). To form longer-chain compounds, the fragments must be reacted to with other such fragments and/or other compounds to form compounds having longer carbon chains. This process is energy-intensive and time-intensive. Further, such processes contributes to the further depletion of non-renewable sources of material. Refining processes for natural oils (e.g., employing metathesis) can lead to compounds having chain lengths closer to those generally desired for chemical intermediates of specialty chemicals (e.g., about 9 to 15 carbon atoms). Thus, refining of natural oils may, in many instances, provide a more chemically efficient and straightforward way to make certain chemical intermediates and specialty chemicals. Further, such processes do not substantially deplete non-renewable sources, such as petroleum. Thus, there is a continuing need to develop processes for making certain chemical intermediates and specialty chemicals using process that employ the refining of natural oils.